Shared spectrum usage by governmental and commercial users has been proposed, e.g. for Citizens Broadband Radio Service (CBRS) specified by the United States Federal Communications Commission (FCC). With shared spectrum usage, a multitude of wireless service providers may utilize such spectrum. Each service provider would employ a system of citizens broadband radio service device(s) (CBSD(s)), e.g. that would facilitate communications with user equipment. The system's CBSDs would be coupled to other networks, such as the Internet, e.g. by a core network.
To encourage frequency allocation efficiency, groups of service providers using a shared access system (SAS) are encouraged to form co-existence groups of CBSDs in a connected set. The CBSDs of the co-existence groups use shared frequency spectrum, and are controlled by the SAS. A connected set means a set of co-existence groups each of which includes CBSD(s) that are allocated the same shared frequency spectrum and are capable of interfering with one another. One or more co-existence groups in a connected set may use different radio access technologies (RATs), where the different RATs have different air interfaces, e.g. as described below.
An interference management policy governs how CBSDs are configured and their transmissions are coordinated to reduce interference amongst CBSDs. A co-existence group means a group of CBSDs which are operated using an interference management policy to mitigate interference amongst the CBSDs in the co-existence group, even if the CBSDs are operated by different service providers. Interference mitigation is desirable because it permits more CBSDs to operate in a frequency spectrum utilized by a SAS.
Typically, the CBSDs in a co-existence group utilize a common RAT with common parameters. For example, CBSDs of a coexistence group with Long Term Evolution (LTE) time division duplexing (TDD) RAT will synchronize their frame timings and the configuration of their uplink/downlink (UL/DL) sub-frame. If the RAT is different between different CBSDs within the connected set, e.g. when using LTE RAT, the CBSDs may not be time synchronized or have the same UL/DL sub-frame configurations. Therefore, a guard band is necessary to avoid interference between adjacent channels.
Each co-existence group would be assigned at least one frequency sub-band within the shared frequency spectrum managed by the SAS. Only CBSD(s) of general authorized access users which are part of the co-existence group would be permitted to operate in the at least one sub-band. Communications systems of incumbent users may also utilize the at least one sub-band.
FIG. 1A illustrates a diagram of one embodiment of a connected set of CBSDs 100A. The connected set of CBSDs 100A comprises a first CBSD 132A, a second CBSD 132B, a third CBSD 132C, a fourth CBSD 132D, a fifth CBSD 132E, a sixth CBSD 132F, a seventh CBSD 132G, a eighth CBSD 132H, and a ninth CBSD 132I. These nine CBSDs can be segregated, as illustrated into a first co-existence group 130A, a second co-existence group 130B, and a third co-existence group 130C.
The first co-existence group consists of the first CBSD 132A, the second CBSD 132B, the third CBSD 132C, and the fourth CBSD 132D. The second co-existence group 130B consists only of the fifth CBSD 132E. The third co-existence group 130C consists of the sixth CBSD 132F, the seventh CBSD 132G, the eighth CBSD 132H and the ninth CBSD 132I. The lines connecting the first co-existence group 130A and the second co-existence group 130B, and the second co-existence group 130B and third co-existence group 130C respectively represent potential interference between the first co-existence group 130A and the second co-existence group 130B, and potential interference between the second co-existence group 130B, and the third co-existence group 130C. The potential interference is the interference created by one co-existence group that is potentially suffered by the other co-existence group. All of the CBSDs in FIG. 1A are part of a connected set of CBSDs 100A.
Larger co-existence groups have relatively more CBSDs than smaller co-existence groups. Generally, the larger co-existence groups require sub-bands (in the SAS shared frequency spectrum) having a larger bandwidth then the sub-bands of smaller co-existence groups. However, smaller co-existence groups require some nominal bandwidth. If there are many smaller co-existence groups, the many smaller co-existence groups may undesirably diminish the bandwidth of a larger co-existence group. Therefore, there is a need to fairly allocate sub-band bandwidth to encourage co-existence groups and to ensure frequency allocation efficiency.